Page 115 - Intro to Space Sciences Spacecraft Applications

Introduction to Space Sciences and Spacecraft Applications
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a. Compute the amount of power that must be radiated from the sur-
face (photosphere) of the sun (E, W/m2) to produce this value at
the earth.
b. Compute the total power output of the sun (W).
c. Using the figures given in the reading and Einstein’s energy/mass
relationship, determine the amount of hydrogen being converted
to helium to produce this power (kghec).
d. Compute how long it will take until the sun uses up half of the
remaining hydrogen.
e. Using the Stefan-Boltzmann relationship, determine the correspond-
ing surface temperature of the sun to produce the power generated.
f. Using Wien’s displacement law, compute the maximum radiated
wavelength associated with this temperature.
3. If the earth were a blackbody with an average temperature of 300 OK,
determine the wavelength of maximum radiation emitted (pm), the
power emitted by the surface of the earth (W/m2), and how much of
this power would impinge on a spacecraft orbiting at geostationary
altitude (W/m2). (rgeOst, = 42,164 km.)

4. Some objects in space are huge emitters of ultraviolet radiation. If a
UV frequency of 3 x 10l6 Hz were detected from a suspected black-
body, determine the temperature and the amount of power emitted by
the surface of this body.